


Contractual Obligations

by Catsitta



Series: Just Business [4]
Category: Undertale (Video Game)
Genre: Alternate Universe - Mob, Alternate Universe - Mobfell (Undertale), Angst, Bara Sans (Undertale), Boss/Employee Relationship, Contracts, Drama, Guns, Implied Sexual Content, Kissing, M/M, Mobfell Sans (Undertale), Power Imbalance, Red is a Mobster, Red is bara, Romance, Sans (Undertale) Has Issues, Sans Has Trust Issues (Undertale), Sans is a Mess (Undertale), Sans is smol, Somebody let him sleep, Sugar Daddy, Sugar Daddy Red, Swearing, Unresolved Emotional Tension, kustard - Freeform, sans just wants to sleep, slowburn
Language: English
Status: Completed
Published: 2021-01-21
Updated: 2021-01-25
Packaged: 2021-03-13 11:28:07
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,571
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28902645
Author URL: https://archiveofourown.org/users/Catsitta/pseuds/Catsitta
Summary: Sans always did say customer service was his calling. But there is an old adage against mixing pleasure with business...Mob Kustard | Slowburn | Romance
Relationships: Sans/Sans (Undertale)
Series: Just Business [4]
Series URL: https://archiveofourown.org/series/2079678
Comments: 67
Kudos: 126





	1. Chapter 1

**Author's Note:**

> This fic is an installment in a series and won't make sense without reading the previous fics.

“well aint yer a sight fer sore eyes. c’mere with that caf and take a seat.”

Sans complied, setting the extra large travel mug of exotic, dark roast coffee on Red’s domineering oak desk, before perching on the edge of an oversized leather chair. Everything in the office was massive, just like the skeleton monster, and none of it was welcoming or relaxed. It was a space meant to intimidate, not invite one to linger. Fortunately, Sans was well-used to Red’s favored decor. If that behemoth of a bed didn’t eat him alive, then the sofa nor the shelves would either. That wasn’t to say there weren’t softer touches if one knew where to look. The rug was ridiculously plush with the most garish, tasteless pattern known to monsterkind. And behind Red’s shoulder, half-tucked behind the books and other clutter, was a framed picture of a babybones about Papyrus’ age...and a rock with a frowny face painted on it.

He watched as Red scooped up his morning order and gulped it down. 

After a nerve-killing first day, where he dealt with weird stares as he followed Red around the office, leaving his side only to bring hot bean juice and meals upon request, Sans was starting to fall into an easy pattern. Wake up. Get Papyrus fed and off to school. Wrestle himself into one of the new button ups in his closet. Then it was off to the fancy coffee shop three blocks away, where he only had to say Red’s name and flash the credit card the monster gave him for work expenses, and he was then to the office. After assuring the lady in the lobby that he was indeed still working for Mr. Fell, he was up the elevator and meandering through a maze of cubicles. For a front for underhanded schemes, it looked real legit. And some of the employees even greeted him on his way to Red’s office once they realized ‘the new guy’ hadn’t been chased off by the bossman. 

Apparently, being a pitiful little shortstack that looked ready to blow over in a stiff breeze made folks worry. Not like Red would just dust an intern for getting his coffee order wrong...right?

Regardless, after coffee, he became Red’s shadow, taking notes when told and otherwise staying out of sight and out of mind. He was being paid to smile, look pretty and pretend to be a useful employee. In private, Red drank up the attention. Sans watched him loom and glower and command, people parting like the sea before him whenever he left his office, with only a brave few (that weren’t ‘business partners’) looking him in the eyes. Thus when the office door shut behind them, it wasn’t uncommon for Red to coax Sans to eat lunch with him, or listen as he talked through his future proposals. It was all...rote. Aside from the occasional flirty greeting or letting his hand linger on Sans’ back or shoulder longer than companionable, the monster behaved himself, seemingly content to leave Sans alone.

“how has yer first week on the job been?” Red asked, voice thick with the last vestiges of sleep. “likin’ the gig so far?”

Sans shrugged and let his eyelights drift to the ceiling, “oh. fine, i suppose. i gotta wear this monkey suit and i’m pretty sure there is a betting pool in the break room on how long it’ll take before i run for the hills.” He peeked at the larger skeleton, “got quite the rep, bossman.”

“how many times do i gotta tell ya, yer don’t gotta call me boss.”

“the face you make when i do is hilarious,” Sans quipped, and Red’s grimace twitched with amusement. “tibia fair, if i call ya red, folks will be making bets of a different kind. and you twitch when i say mr. fell too.”

“don’t understand why yer worried ‘bout a little talk.”

“it’s generally frowned upon to be seen as the guy probably banging the boss. employee relations one-o-one right there.”

Red snorted and took a long sip of what remained of his coffee, “screw’em. not like their opinion matters. and it wuz yer idea to do this whole personal aide, intern, secretary or whatever shtick. if they find out we’re fucking, what’s it change? i wanted to introduce yer as—”

“red...we talked about this.”

“yeah, we did, and i followed the contract to the letter, didn’t i?” he snarked, his humor souring. “doesn’t mean i think it’s any less stupid to act like we’re strangers.” As clawed phalanges tightened around the cup, Sans shivered, starkly aware of his LV. After all this time, he was mostly used to the eerie feeling of Red’s aura and magic, but when his moods darkened, it was impossible to ignore. He was like a walking blizzard or a barely civilized predator on the prowl. And Sans was a wet paper towel that would rip at the slightest hint of violence. Years of customer service and months of learning what made Red tick, allowed Sans to keep his composure, his smile firmly in place, his posture deceptively lax. A bead of sweat dribbled down the back of his neck. 

“it is called reputation. i’d like to keep some semblance of one intact,” Sans said. “if this doesn’t work out and i need to find a new job—”

“yer don’t even gotta do this job!” Red snapped, one hand hitting the top of his desk, the force knocking over a cup of pens. Call it fried nerves from running on empty for so long, unable to get a proper night’s sleep, but Sans flinched. The sharpness in his voice. The impact of his hand on the desk. That latest uptick in LV. All combined sent a bolt of panic through an overworked system. “...sans?”

He peeled open a socket he didn’t even realize he’d clamped shut and tried to laugh it off. He wasn’t paid to be a skittish little lamb that cowered every time Red’s temper got the best of him. 

“dammit...i scared ya, didn’t i?”

“nah. me, scared of you? never. you’ve never hurt me.” _Not yet, at least._

Red curled his phalanges into a ball, staring at his ring-laden hands like they’d betrayed him. From what Sans remembered from highschool biology, LV did funny things to the soul. It hardened one against compassion and made it hard to experience empathy. It distanced one from the suffering of others. The more one hurt others, the thicker the callous, and the easier it became. Monsters and humans alike could lose their sanity to too much LV. It tainted one’s magic and warped the soul. And there was no cure.

_you should have never accepted that first date. you should have never gotten yourself mixed up with someone like him. now look at you? in over your head with no easy way out unless your patron decides to pop your skull off your neck._

“...sorry,” Red mumbled. “i don’t want yer to ever be afraid of me, sweetheart.”

“thought i told you that ya didn’t scare me?” Sans sassed, crossing his arms. The lie was bittersweet on his tongue. “i’ve been in food and customer service my whole adult life. think i can’t handle somebody raising their voice a little when they’re frustrated?”

A small chuckle escaped Red, “yer can handle yerself jus’ fine. i remember the first time i tried to, ah...help. ya about chewed my head right off.”

“well you were making things worse with your big-tough-and-scary act. doggo was drunk and just lost at poker. i’d handled his temper tantrums for years, and you just made his hackles raise and start barking louder.”

“how wuz i supposed to know the mutt was half blind and didn’t realize i wuz twice his size?”

“wouldn’t have mattered if you’d stayed in your seat like a good boy.”

A wicked grin split Red’s skull, and his browbrowns slanted with mischief, “we both know i’m no good.” Sans leaned a little forward, noting how the other’s foul mood was replaced with something far more familiar, but did little to put him at ease. Red motioned for Sans to come closer, and Sans swallowed. “c’mere. i’ve been a bad, bad boy.”

“hm...how about no?” Sans stood up, ambling around his desk in direct contradiction to his own protest. “when you’re bad, you get punished. aint that how it goes?”

“oh i’m bein’ punished alright,” Red muttered. “stars, i want you.”

Those words made him freeze. 

He was close enough for Red to reach out and grab, easily scooping him onto his lap.

This was it. 

This was when Red ignored the line Sans drew in the sand because he knew he could get away with it. Sans wouldn’t raise too much fuss. As humiliating as it would be to start his work day helping the boss get his rocks off, it would be like ripping off a bandaid. Maybe Red would even let him go home early with some extra cash tucked in his front pocket, so he could ‘prepare’ for the party late that evening. 

A hand settled warm on his hip. 

Maybe he would let Sans pleasure him with his mouth and would leave his clothes unruffled. It would be so hard to look his new coworkers in the eye if Red pushed him flat on his back on the sofa and divested him of his trousers. 

_pathetic little whore._

Sans’ soul skipped a beat and he shoved his anxiety down. He squashed it until it sat like a lump in his gut to choke on later. Just like when he first slept with Red. The fact the other was considerate and made his body sing made every subsequent visit all the easier. He tilted his head up, trying to muster up the words to either turn Red’s advances down or convince them both that Sans wanted a romp in the office. But then Red spoke.

“but no startin’ any funny business,” he said with a sigh. “not here or in the car or anywheres yer don’t like unless yer give the okay. nothin’ in the contract against kissin’ yer silly, though.”

“o-oh. there isn’t...is there?”

Red nuzzled his neck, “loopholes are a bitch, aren’t they? hmmmm. now, speaking of contracts...i believe i’m scheduled in that little calendar of yours from 7pm until 7am~?” 

“y-yeah. black tie. the dreemur’s are hosting a gala for their kid’s coming of age or somethin’ like that.”

“so organized. no wonder i hired you to be my personal assistant~” He caught Sans’ mouth with his own, the kiss firm and familiar. A less than professional grope to the tailbone later, and Sans was free, his fears unrealized. “speaking of which, have yer seen my stapler anywheres?”

Sans blinked back into reality and tried to ignore the way his whole body trembled.

He really was so very, very tired.

So tired, in fact, that after a day of running errands as per the new usual, he forgot to protest when Red offered to take him home after work. Habits born of old and worn routine, he fell in step beside the other, blissfully spaced out on the walk to the car, forgetting for a moment that he lived a hop and a skip away. And as he settled in the car, Red tugging him close, his lids grew heavy. Maybe Red would decide to duck out early on the party and just have his way with him so that he could get some sleep. That would be nice. Just some lazy, end of the week sex in Red’s big bed while buzzed on campagne and fruity cocktails to bring some normalcy back into his life. 

Papyrus was sleeping over at Undyne’s again. No need to worry about him unless he called since Gerson was a good guardian. He hated to impose of him but...if this thing with him and Red really was going to be long term…

“wakey-wakey sleepin’ beauty.”

“hn?” Sans rubbed his sockets. Oh. Red hadn’t taken him to his condo, but to Red’s house. Well, he supposed that worked. He must have clothes for Sans to wear. When he began ushering Sans out of the car, Sans couldn’t help but to groan, “hnnnng. slave driver.”

“don’t worry. yer can nap before the party. i’ll wake yer up when yer need to get dressed.”

And true to his word. He did. He left Sans unmolested in his bedroom, curled up in the middle of the sheets, dead to the world for all of an hour, before rousing him with a nudge and a kiss. As he blinked away from his dreamless sleep, he caught Red’s unguarded stare, so different from the usual possessiveness and desire. His want was soft around the edges and warm like innocence. It a look his eyelights begged the question, _Why not make this forever and always?_

They both knew why.

Even if Red didn’t know Sans knew what he got up to when he wasn’t growling at pencil pushers in a high rise. 

A comfortable calm settled between them as they headed for the party, hands roaming just a little, flirty but not demanding. And by the time they stepped out of the car, the both of them were smiling, their chosen masks in place. Red wearing a devil-may-care grin with brimstone in his eyes and Sans soft, unassuming and placid at his side. They knew this act by heart.

But after a round of hors d'oeuvres and only a few sips of wine, normality was shattered by a gunshot and the hostess herself wailing in horror.


	2. Chapter 2

In a snapshot of reality, between blinks and before the world took in a collective breath, the scene laid plain before all in the ballroom. Toriel Dreemur curled over the limp and bloodied form of their adopted human child, healing magic casting an emerald glow. Behind her stood the monster of the hour, Asriel Dreemur, for whom the gala was being held to celebrate his coming of age—his expression dull with shock, his white fur spattered with red, as he stared at his sibling’s unmoving body. To his left was his father, Asgore Dreemur, one paw in motion to push Asriel behind him, the other reaching out for his wife, his aura vast and frigid. It was said that the Dreemurs were among the oldest of the monsters, their bloodline that of the royals of yore, with Asgore himself being a survivor from an era when monsters were at war with humanity. 

Time returned in a thunderclap.

Guests—monster and human alike—scrambled for safety, voices raised with panic. Toriel wailed again in despair as she soaked Chara’s unmoving body in green. Asgore mouthed something to his son, but Asriel remained stiff, frozen in place, only moving when his father tried to push him away. The elder Dreemur child shook his head and reached for his mother and sibling, refusing to flee to safety. Suddenly, Asgore’s head snapped up and Sans realized who he was looking at. 

Red.

The pair locked eyes and with a look and a nod, something of an order or a request was given. He wasn’t sure what exactly. Because he didn’t know how well Red knew the Dreemurs or if they were mixed up in the same underworld affairs. All he did know was that Red turned and shoved him under a table a second later, expression raw with conflict for a soulbeat. Clawed phalanges traced his face like he was precious and fragile, a porcelain doll that would be so easily cracked or shattered. Then he pulled back.

“keep yer eyes shut,” Red ordered, voice low. “don’t listen or look. don’t go nowheres. just stay here, outta sight, and yer will be fine.”

Sans almost asked why. He almost dared break the soft illusion he allowed himself—that paperthin denial. Red should be scared. If he was a businessman, he should have run screaming like many of the other guests. He should have climbed under that table with Sans and held him close as they waited for help to come. But he doesn’t. And Sans doesn’t ask him to. He doesn’t question why, because he knows the answer. He kept his mouth shut and nodded as Red dropped the edge of the table cloth to hide him from sight. 

Sheltered in the shadows of the table, only a halo of indirect light creeping beneath the edge of the cloth, Sans waited. He waited and against Red’s orders, he listened. It was chaos. People were rushing around, the air thick with a palatable tang of terror. There was a shout to let them out. Another to keep everyone in. There was an outcry for authorities, somebody hysterically pleaded for the police. A woman wept. A man shouted. Beneath it all was Toriel begging Chara to keep breathing. To hang on. Telling them they would be okay and to not give up.

It should have been easy to remain hidden. To keep curled up in a ball as Red did whatever it was Asgore silently asked him to do. But as the minutes ticked onward, his phalanges crept closer to the edge of the cloth. And eventually, he pulled it up just enough to peek out from under. Spotting Red was simple. He towered over most of the guests and waded through them like a ship through a churning sea. But what he didn’t expect to spot was a human with higher LV than those around him. Out of reflex, he let his gaze linger, focused on the hazy numbers and words until they formed a sensible block of stats. 

His soul dropped to his proverbial stomach.

_*His mission failed—he is looking for an escape._

Not his horse and not his race. Beyond misguided altruism, Sans had no reason to involve himself in the middle of this fiasco. Sure, somebody might have just died and this person might get away if he did nothing...but who was he to intervene? Nobody! Heroics wasn’t his thing. He was the kind of guy to just sit back and let other people handle the big, important stuff. He wasn’t going to put himself in danger—

An image of Papyrus’ sweet, trusting smile flashed in his mind. All bundled up in a scarf and a parka that was far too large. He saw him reaching out to the wrong stranger with hope in his eyes. Saw his smile ripped from the world in a cloud of dust, his killer walking away free, faceless, no witness coming forth.

—but if he didn’t, the person that shot the youngest Dreemur would possibly escape without consequence. They could go on to hurt other innocents. 

_hypocrite, if you really cared about that you wouldn’t be sleeping with the devil because he made you a cushy little deal._

Sans never claimed to be a saint.

Or a hero.

Or smart.

Digging down deep, he formed a pattern of bullets, small and almost ghostly. His aim wasn’t to do harm, but to stall. With a flick of his command hand, a tiny, erratic wave of little bones jutted out beneath the gunman’s feet. The first made him stumble. The second made him flounder. And the next sent him cussing and crashing into a nearby table, empty wine glasses shattering as the weight of the impact sent everything to the floor. There. That was enough. Sans watched the gunman’s HP trickle down, a side effect of his attack magic that made him leery of ever getting into a fight. How easy it would be to accidentally kill someone. Even if his every bullet only did a single point of damage, depending on the LV of his opponent, there would be a continued drain of HoPe. 

He didn’t have an answer as to why his magic acted like poison. Why it festered and burned and corroded. His father tried to assure him that it wasn’t a bad thing with a plastered on smile as he pulled a shattered fragment from his arm when Sans’ had his first magical outburst. That it just meant he could protect himself from bad people. But Sans wasn’t a fighter. Why would he, of all monsters, manifest such power? To be able to see the Truth of a person, down to their stats, and then to hurt them for hurting others. Like...who was he to Judge anyone for their mistakes? Their shame? Their sins?

He was just...Sans.

As the gunman struggled to his feet, there was a change in his posture, in his demeanor. His breathing was rapid, his hand clawed at his chest and then, he bolted, his composure shattered. Shouts went up and all eyes were on the would be assassin. He wasn’t going to get away. And he wouldn’t hurt anyone else. 

Sans didn’t even notice he had crawled from under the table until he was already standing, gaze settled on Red and some equally beefy monsters as they stalked their way towards the man. His soul fluttered a bit. No. This was NOT the time to think about how unreasonably arousing it was to see Red all mean and snarly, knowing full well how soft he could touch, how sweet he could plead. Good grief. Sans decided to blame it on fear and the whole close-to-death experience. He probably wasn’t the only one with itchy magic now that the danger had...passed…

His drifting gaze fell upon another human in the back of the crowd, face impassive, utterly nondescript and unassuming if one couldn’t SEE their malevolent intent and the way their gaze was unnaturally fixated on Red. Sans scarcely noticed most of their stats save a couple key bits.

LV 6  
 _*The world would be better without monsters, especially that skeleton menace._

Intent mattered when one set out to do harm, especially upon a monster. And if that human attacked Red, there would be only dust. Monsters, even powerful monsters, were terribly vulnerable to others’ desire to hurt them. Even a child with a stick or a toy knife could slay the best of them if they harbored enough hatred and determination to kill in their heart. 

The human lifted up a gun.

BANG.

People screamed and turned to see a single bone attack jutting through the floor, the gunshot sent wildly off course and the weapon thrown from the assailant’s hand. And said assailant? He was face first on the marble floor, pinned there by blue magic encasing his soul, nose and mouth bleeding from being bounced— _hard_. A pair of the beefy monsters (that Sans absently realized had to be plainclothes security for the Dreemurs) secured the second gunman. 

“yer can let go, sweetheart.” It was Red. He was murmuring placations and gingerly, as if he was a feral cat, touching, then rubbing Sans’ shoulders and arms. “yer safe. yer can calm down now. the authorities are comin’.” How could he know it was safe? There could be others. There could be more of them. “shhhh. easy, dollface, i know yer scared, but i need ya to come back to me.” Scared? Sans was distantly aware of the sweat beading down his skull and the unsteadiness of his hand. Of his whole body. He was shaking. “let go.”

Sans obeyed.

His hold on the human’s soul released and he slumped against Red, who drew him into his chest. Red simply held him for a moment, hard and tight. “what the hell were ya thinkin’?” he hissed, not in anger, no. That wasn’t quite right. “i toldja to stay under the table.”

“...he was going to shoot you,” Sans mumbled, avoiding the heart of the question. 

“what?”

“i saved your life, asshole.”

Red didn’t respond right away, but his soulbeat quickened, as if suddenly all too aware of his own mortality. He gave a small, weak chuckle, “why didja do that? if i wuz dust, yer coulda lived out the next few years comfortably in that condo even without workin’.”

Sans scoffed and didn’t answer. He couldn’t. He wasn’t sure if he had one. He could have—should have—let Red die. No more contracts. No more worries about Red getting violent or bored. No more lying to Papyrus about what he did on the weekends or how they afforded turning their life around. It was the legal loophole in the contract that Sans pointedly wrote in just in case Red’s career choice caught up with him. 

It did today. 

And Sans intervened. 

Like. An. Idiot.

“and _you_ thought i was paranoid to have that ‘in case of death’ clause in the contract.”

“...heh...aint that the damn truth,” Red quipped, his voice husky. “guess i was expectin’ to find poison in my morning coffee, not...this…”

“how badly were you plannin’ to piss me off? i mean, you’re obnoxious sometimes, but c’mon, everyone knows coffee is sacred. and honestly, if i was gonna dust ya for the money, it woulda been more fiscally responsible to, uh...well, accept the other contract first. maximize my profits and all that. you know me, it’s...it’s all about the money.”

Red sputtered out a laugh, “true. true. always business wit yer.”

“yeah...just business.”

_“If I may interrupt?”_

Both skeletons broke from the embrace to look up at the host of the gala. Red cleared his throat and stood a little taller, shoulders straight, any and all sappiness gone. Sans was, uh, less put together. But he had practice with masks and offered his best, nonchalant grin, prepared to be the silent accessory.

Asgore nodded and offered a paw to Sans in greeting, “I do not believe we have met. I am Asgore Dreemur. I wish to offer my apologies as well as my thanks. Your actions today prevented further casualties.” Sans reluctantly shook his hand. “Might I inquire to your...association with Mr. Fell? I have seen the two of you together at prior events and assumed...well, regardless of that, are you part of his security? He’s not known for keeping a bodyguard around for very long.” His look was telling. Red apparently had one helluva reputation of being hard to work for. 

“sans and i should head out. it has been a long day.”

“uh...shouldn’t we stay to talk with the police or whatever?”

Asgore offered a strained smile, “I see. Well, I must bid you goodnight. The both of you. I have important matters to attend to.” 

They all looked over to where Toriel sat, her tears happy ones as she held a weak, but very much alive Chara in her arms. The kid needed to go to the hospital, but they weren’t pushing up daisies yet. Sans watched as Asriel tried to offer comfort, but Chara gave their brother a glare of pure sibling annoyance and swatted at him halfheartedly. Asriel beamed. 

And all of Sans’ danger fueled energy abandoned him as reality dawned, bright and painfully blinding. He protected Red—an objectively bad monster with countless sins resting on his soul. A monster that loved him. A monster the world would have been better off without. A monster to whom Sans’ obligations did not go beyond what was written in ink. And yet—

He swayed and his companion caught him.

—Sans saved Red's life.

**Notes for the Chapter:**

> AUTHOR'S NOTE:  
> In a detail that is only as relevant as you want it to be (as it is something Sans doesn't know) is that the hit was on Asriel. Chara pushed him out of the way before the gun was fired, as they don't have magic.

**Author's Note:**

> Another installment? And a two-parter at that? Le gasp!


End file.
